Weedy and Invasive Plant Genomics

Book Preface

Genomics does not provide any information that cannot be obtained by more traditional genetic approaches. However, traditional approaches analyze one or a few genes at a time. Among other things, genomics seeks to examine the response of the entire genome to a given stimuli — in one of the most pertinent cases in weed science, an herbicide. A better understanding and use of these technologies potentially allows the weed scientist to fi nd new herbicides and herbicide mechanisms – of – action and extend the use of current herbicide mechanisms – of – action by overcoming weed resistance, developing crop resistance, or making them more effi cacious. Weed scientists and those interested in controlling invasive plants face many challenges concerning available control techniques. When examining chemical control of weeds, there are three major issues facing weed scientists: (1) resistance of weeds to existing herbicide mechanisms – of – action, (2) loss of older herbicides, and especially specifi c herbicide mechanisms – of – action (MOA) through regulatory or economic means, and (3) lack of new herbicides, and especially herbicides with novel mechanisms – of – action.

When we examine the past decade in weed science, we see a revolution in weed control through the introduction of herbicide – resistant crops. Currently, in the U.S., between 50% and 75% of the major grain, oilseed, and fi ber crops have either an herbicide resistance trait or an insecticide trait, or in some cases, both (Dill et al. 2008 ). The rapid adoption of herbicide – resistant crops has had many positive impacts on weed management, but it has also led to some troubling trends. The widespread reliance on a few herbicides for weed control in the major row crops has led to downward price pressure on other herbicides, which has contributed to industry consolidation. The lower return on investment of newer herbicides has been a contributing factor in fewer herbicide introductions and the lack of new herbicide mechanisms – of – action since 1993 (Kraehmer et al. 2007 ).

In some major row crops, such as soybeans and cotton, there has been an overreliance on one herbicide for weed control that has created high selection pressure for resistance development. The conundrum is thus: if widespread resistance occurs to the most commonly used herbicides and we have fewer older herbicides available because of regulatory issues and economic reasons, and there are fewer herbicides and new herbicide mechanisms – of – action in the pipeline, are we far from having a scenario in which we have no herbicides available for certain crops? Furthermore this scenario is building at a time of increasing demand because of population growth, more affl uence in the developing world with its modernization of agriculture, and biofuel demand. For a weed scientist, it is obvious that many of the technologies such as screening thousands of organic compounds a year to discover a potential herbicide, which has provided new herbicides and herbicide mechanisms – of – action in the past, might not be viable in the future. Many genomic technologies could provide methods of obtaining the new herbicides and even new classes of herbicides that are the cornerstone of modern weed control.